As always, visiting the MSDN documentation first should be the way to find information. The documentation for the CInt function has this to say:
If the fractional part is exactly 0.5, the integer conversion functions round it to the nearest even integer. For example, 0.5 rounds to 0, and 1.5 and 2.5 both round to 2. This is sometimes called banker's rounding, and its purpose is to compensate for a bias that could accumulate when adding many such numbers together.
A quick look at the documentation for the Math.Round method reveals that it uses banker's rounding too.